Boeing will deliver its 4,000th 737NG, a -700 variant of the narrowbody aircraft, to China Southern Airlines this week.

The aircraft, which rolled off the 737 production line at Renton in Washington, was handed over to the SkyTeam alliance member in a special ceremony over the weekend.

It will be flown from the US to the airline’s Guangzhou base on Tuesday, 15 April 2012.

“It is an incredible milestone to be delivering our 4,000th 737NG. We thank China Southern Airlines and all our customers who have made the 737 the world’s most popular jetliner,” says Beverly Wyse, vice-president and general manager of the 737 programme.

The airframer says that the gap between each record 737NG delivery is shrinking. It took three years and one month between the 2,000th and 3,000th, but two years and eight months between the 3,000th and 4,000th delivery.

“With 737 production rates increasing incrementally to a record 42 airplanes a month in the first half of 2014, the gap will continue to close,” says Boeing.

The 737NG has won more than 6,600 orders and has a backlog exceeding 2,600 airplanes.

There are more than 5,550 737s in service globally, including the Classic and NG variant, says Boeing. They are operated by more than 358 airlines in 114 countries.

China Southern has another 45 737-700/-800s on order. The 737 that the SkyTeam alliance member will receive this week can seat up to 126 passengers in a two-class configuration and features the new Boeing Sky Interior.

The aircraft will be the 75th 737 to be delivered directly to the company.